Patent EA-001606-B1 (EA)
Title: Electrochemical machinning a workpiece
Inventor: ALTENA HERMANUS S J
IPC: B23H7/16
Filed: 1999-01-11
Abstract: 1. A method of electrochemically machining a workpiece by means of an electrode, said method comprising the steps of: - setting a gap between the electrode and the workpiece, which gap is flushed with an electrolyte, - feeding an electric current through the electrolyte in the gap via the electrode and the workpiece in order to machine the workpiece, - generating a measurement signal comprising information about possible spark discharges in the gap, and - protecting the electrode and/or the workpiece against damage by reducing the current when a parameter of the measurement signal exceeds a certain threshold value, characterized in that, the measurement signal is generated by means of an antenna for detecting HF electromagnetic waves originating from the gap. 2. A method according to claim 1, characterized in that said parameter is the amplitude of the measurement signal in a high frequency band. 3. A method according to claim 1, characterized in that said parameter is the amount of energy in a high frequency band. 4. A method according to claim 1, characterized in that the threshold value is determined from observations of the measurement signal in a time slot preceding the occurrence of a spark. 5. An apparatus for electrochemically machining a workpiece by means of an electrode, said apparatus comprising: - an actuator for setting a gap between the electrode and the workpiece, - fluid transport means for flushing the gap with an electrolyte, - power supply means for feeding an electric current through the electrolyte in the gap via the electrode and the workpiece in order to machine the workpiece and damage prevention means comprising: - measurement means for generating a measurement signal comprising information about possible spark discharges in the gap, - detection means for generating a stop signal when a parameter of the measurement signal exceeds a threshold value, and - reduction means for reducing said current upon detection of said stop signal, characterized in that, the measurement means comprises an antenna for detecting HF electromagnetic waves originating from the gap. 6. An apparatus according to claim 5, characterized in that the antenna is electrically isolated from the electrode and the workpiece. 7. An apparatus according to claim 5, characterized in that the antenna is a dipole antenna. 8. An apparatus according to claim 5, characterized in that the antenna is a loop antenna positioned around the gap. 9. An apparatus according to claim 5, characterized in that the detection means comprise a band-pass filter followed by a level detector to detect the level of the measurement signal in a frequency band between 10 and 100 MHz. 10. A damage prevention means comprising: - measurement means for generating a measurement signal comprising information about possible spark discharges in an inter-electrode gap, - detection means for generating a stop signal when a parameter of the measurement signal exceeds a threshold value, and - reduction means for reducing said current upon detection of said stop signal, characterized in that, the measurement means comprises an antenna for detecting HF electromagnetic waves originating from the inter-electrode gap.